Wall systems, and particularly retaining wall systems, which are derived from stackable interlocking modular precast concrete blocks that include facing wall units or stretchers, tie-back units or headers or combinations of same which go to make up cribbing units are well known.
One early gravity retaining wall system is disclosed by Canadian patent no. 941626 constructed from several like sets of blocks including facing wall units or stretchers and tie-back units or headers which have axially aligned matching projections and recesses so as to establish a strong sliding fit connection between inferior and superior courses one upon the other in which there is no setback and which are preferably, if not necessarily, mounted upon a rearwardly angled prepared footing.
Another proposal includes selecting appropriate dimensions for the modular blocks of the sets of units and adopting desired positioning of respective projections and recesses, as described by U.S. Pat. Nos. 4,490,075 and 4,815,897, which produces a precisely inclined facing wall or a vertically extending facing wall or a combination of inclined and vertically extending wall sections, all overlapped and interlocking in sliding fit in stacked relation without the use of mortar and all to be mounted upon a generally horizontally extending prepared footing.
The mortarless gravity retaining wall systems derived from the modular blocks that include facing wall units or stretchers and tie-back units or headers or the combinations thereof found in U.S. Pat. Nos. 4,490,075 and 4,815,897, utilize fixed offset projections and recesses for establishing a secure sliding fit interlock for respective modular blocks of the stacked superior and inferior courses and are limited to the degree of offset selected or the combination of such selected offset that produces two specific dispositions between superior and inferior blocks, namely, a specific angle of inclination and a generally vertical disposition of the facing wall, all in the manner prescribed by the United States patents above identified.
According to another proposal, U.S. Pat. No. 3,680,277, an arrangement for connecting stackable units such as concrete blocks or clay bricks together is disclosed wherein the blocks or bricks are provided with dovetail grooves or channels arranged in opposition. When like blocks are placed end-to-end with the respective opposed dovetailed grooves of such blocks adjacent to one another to form a keyway, a suitably dimensioned flexible springlike strip, folded upon itself, is fitted within the keyway so defined whereby adjacent blocks are secured together against separation.